Disc drives are store digital data in magnetic form on a rotating data storage disc. Modern disc drives comprise one or more rigid data storage discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks (collectively referred to as the “data region”) typically by an array of transducers (“read/write heads”) mounted to a radial actuator for movement of the heads in an arc over the surface of the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write heads are used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to a host computing system.
The transducers or heads are mounted on sliders via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Rotary actuator assemblies typically employ a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted at one end of the actuator body opposite the actuator arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces. The actuator assembly thus allows the head to move back and forth in an accurate fashion between an inner diameter (ID) and an outer diameter (OD) of the discs.
A printed circuit board assembly (“PCB”), which is mounted to a bottom surface or base plate of the disc drive, contains a majority of the electronics that are essential to the operation of the disc drive. For example, the PCB includes electrical components that control the speed of the spindle and position of the heads over the discs. Similarly, the PCB also includes electrical components that interface with the host computing system.
When the disc drive is de-energized, the PCB automatically moves the heads to a circumferential storage location or “park” location on the disc surfaces. The park location is typically located about an inner diameter or outer diameter of the data storage region of the disc and is typically called a landing or parking zone. This parking zone typically does not contain any useable data because the transducer physically contacts the disc at rest. Consequently, any data stored in this area would likely be lost or compromised by physical contact with the read/write head. In addition, the parking zone is typically roughened to minimize the stiction of the transducer against the disc surface.
Alternatively, disc drives may utilize load/unload ramps to facilitate removal of the heads from the discs to a parked position adjacent the discs. A load/unload ramp in a disc drive is typically stationary, such that in the process of the actuator assemblies being unloaded from the disc, the heads are moved to the outer rim portion of the discs so that a guide pin extending from the suspension engages the ramp and lifts the heads off the disc surface. The suspension and attached heads then traverse up the load/unload ramps to a park location a safe distance away from the disc surfaces. In the reverse process, the heads are loaded onto the spinning discs by the suspensions and attached heads moving down the stationary ramps and onto the media.
During periods of inactivity (i.e., power down), the fragile magnetic coating on the surface of the disc is susceptible to damage from accidental contact between the head and the data region of the disc if the head is accidentally displaced from the parking zone. Repeated failure to properly park the actuator assembly causes various problems, including scratches to fragile magnetic coating on the discs, damage to the transducers, and stiction between the transducer and the disc during operation, all of which may ultimately lead to a disc drive “crash.” Thus, any failure to properly park the actuator assembly in the parking zone when the disc drive is powered down can be detrimental to disc drive performance.
Despite the detrimental effects of such parking errors, most parking failures will not be discovered by a user until the damage is severe, such as where disc sectors have been irreparably damaged or the disc drive crashes. Unfortunately, by this time, the damage is irreversible. Further, without prior notice of potential problems, the user will not have the opportunity to backup or otherwise protect valuable data.
Accordingly there is a need to provide computer users with notice when the actuator assembly does not properly park in the parking zone as a disc drive is powered down. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.